ambassador to libya and three other americans were killed at the u.s. consulate in benghazi. tonight, a rare reversal, tonight, the intelligence officials say they originally got it wrong. patience, with the investigation, and shifting explanations from the administration. tonight, members of congress from both parties are demanding answers, and on the ground in libya, the american officials sent to piece this case together can't even get to the scene of the attack. we begin tonight with our justice correspondent, pete williams in washington, good evening. >> reporter: savannah, it is a very unusual statement, the top officials admitted today that the attacks that were spontaneous were wrong, but getting answers to exactly what did happen has not been that easy. the u.s. understanding of what happened in libya said a spokesperson for the director of national intelligence continues to evolve. tonight, the dni says "we revised our initial assessment to reflect the intelligence." they believe it was an organized attack, and some involved were linked with groups with al-qaeda. bu